package com.jsyl.infra.utils.encrypt;

import java.io.ByteArrayOutputStream;

public class Base64 {
   private static char[] base64EncodeChars = new char[] { 
	   'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 
	   'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',  
       'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',  
	   'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',  
	   'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',  
	   'o', 'p', 'q', 'r', 's', 't', 'u', 'v',  
	   'w', 'x', 'y', 'z', '0', '1', '2', '3',  
	   '4', '5', '6', '7', '8', '9', '+', '/' };  
   private static byte[] base64DecodeChars = new byte[] {  
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  
	    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,  
		52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,  
		-1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,  
		15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,  
	    -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,  
		41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1 };  
		  
   private Base64() {}  
		/**
		 * 数据加密编码  
		 * @param data 要加密的字节数组
		 * @return 加密后的字符串
		 */
	   public static String encode(byte[] data) {  
		   StringBuffer sb = new StringBuffer();  
		   int len = data.length;  
		   int i = 0;  
	       int b1, b2, b3;  
	       while (i < len) {  
	          b1 = data[i++] & 0xff;  
		           if (i == len) {  
		               sb.append(base64EncodeChars[b1 >>> 2]);  
		               sb.append(base64EncodeChars[(b1 & 0x3) << 4]);  
	                   sb.append("==");  
		               break;  
		            }  
		      b2 = data[i++] & 0xff;  
		           if (i == len) {  
		              sb.append(base64EncodeChars[b1 >>> 2]);  
		              sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);  
		              sb.append(base64EncodeChars[(b2 & 0x0f) << 2]);  
	                  sb.append("=");  
		              break;  
		            }  
		     b3 = data[i++] & 0xff;  
		     sb.append(base64EncodeChars[b1 >>> 2]);  
		     sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);  
		     sb.append(base64EncodeChars[((b2 & 0x0f) << 2) | ((b3 & 0xc0) >>> 6)]);  
		     sb.append(base64EncodeChars[b3 & 0x3f]);  
		    }  
		       return sb.toString();  
		   }  
	   /**
		 * 数据解密 
		 * @param data 要解密的字符串
		 * @return 解密后的byte[]数组
		 */  
	  public static byte[] decode(String str) {  
		       byte[] data = str.getBytes();  
		       int len = data.length;  
		       ByteArrayOutputStream buf = new ByteArrayOutputStream(len);  
	           int i = 0;  
		       int b1, b2, b3, b4;  
		       while (i < len) {  
		    	   /* b1 */  
		           do {  
		                b1 = base64DecodeChars[data[i++]];  
		              } while (i < len && b1 == -1);  
	                if (b1 == -1) break;  
		  
		           /* b2 */  
		           do {  
		                b2 = base64DecodeChars[data[i++]];  
		            } while (i < len && b2 == -1);  
		          if (b2 == -1) break;   
	               
		          buf.write((int) ((b1 << 2) | ((b2 & 0x30) >>> 4)));  
		  
		           /* b3 */  
		           do {  
		               b3 = data[i++];  
		               if (b3 == 61) 
		                   return buf.toByteArray();   
		                b3 = base64DecodeChars[b3];  
	               } while (i < len && b3 == -1);  
		          if (b3 == -1) break;  
	              
		          buf.write((int) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));  
		  
	            /* b4 */  
		          do {  
		               b4 = data[i++];  
		               if (b4 == 61)
		                    return buf.toByteArray();   
	                b4 = base64DecodeChars[b4];  
		           } while (i < len && b4 == -1);  
	             if (b4 == -1) break;  
		          
	             buf.write((int) (((b3 & 0x03) << 6) | b4));  
		       }  
		        return buf.toByteArray();  
		   }  
		}
